12-Aminododecanoic acid as a corrosion inhibitor for carbon steel

The inhibiting effect of 12-aminododecanoic acid (AA) on corrosion of carbon steel (CS) was investigated in hydrochloric acid of different pH, temperatures and over a prolonged period of time, and also in some other selected corrosive solutions. It was found that AA inhibits both partial corrosion reactions, with a slightly stronger inhibition of the anodic corrosion reaction. The corrosion protection mechanism is by formation of a surface-adsorbed AA monolayer that offers a hydrophobic barrier to transport of solvated corrosive ions to the surface. A maximum inhibition efficiency of 98.8 ± 0.5% was achieved in 0.5 M HCl. The adsorption of AA onto the CS surface was described by the Langmuir adsorption isotherm. The corresponding standard Gibbs energy of adsorption was calculated to be −26 kJ mol⁻¹. Polarization modulation infrared reflection absorption spectroscopy measurements revealed that the adsorbed AA monolayer is amorphous, which is due to the high heterogeneity of the CS surface.     

Soluble conducting poly(aniline-co-orthotoluidine) copolymer as corrosion inhibitor for carbon steel in 3% NaCl solution

The copolymer poly (aniline-co-o-toluidine) noted poly(ANI-co-OT) is chemically synthesized, and characterized by FT-IR, UV-Vis, TGA and XRD techniques. The results show that this copolymer presents new structures and it is more thermally stable than the corresponding parent homopolymers. It is found that it is soluble in dimethylformamide (DMF), while the homopolymers have a low solubility. Techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) have been employed to study the inhibition effects of this copolymer on the corrosion of carbon steel in 3% NaCl solution. The results show an increase in inhibition efficiency as a function of copolymer concentration to attain an optimum (70%) for a concentration close to 100 ppm. This is due to the higher coverage of the carbon steel electrode surface as shown by the Temkin adsorption isotherm. The Potentiodynamic polarisation studies reveal that this copolymer acts as a mixed-type inhibitor. The results obtained by potentiodynamic and EIS techniques are in good agreement.     

Underscale corrosion behavior of carbon steel in a NaCl solution using a new occluded cavity cell for simulation

A new occluded corrosion cavity (OCC) simulation cell was designed to study the underscale corrosion behavior of carbon steel (N80) in 0.2 mol L⁻¹ NaCl solution. The chemical components of the solution in the OCC were measured and the electrochemical behavior of the occluded anode and the bulk cathode were studied by electrochemical impedance spectroscopy (EIS). The newly designed OCC cell can easily simulate the auto-catalyzing acidification process and may be used to study the mechanism of underscale corrosion. The corrosion scale exacerbates the underscale corrosion and the area ratio of the bulk cathode to the occluded anode (R = S_c/S_a) determines the development of simulated localized corrosion in the OCC cell. When R was within a certain range, the corrosion rate in the OCC could be kept at a persistently high level. The pH of the solution in the OCC decreased and the chloride ions (Cl⁻) concentrated as the local corrosion developed. The anodic process on the occluded anode was controlled by irreversible charge transfer and the cathodic process on the bulk cathode was controlled mainly by oxygen diffusion.     

Temperature dependence of the electrochemical corrosion characteristics of carbon steel in a salty soil

The electrochemical corrosion characteristics of carbon steel in a salty soil at different temperatures were studied by measurements and analyses of potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy. The results showed that the mass-transfer of dissolved oxygen plays an essential role in carbon steel corrosion, and the whole corrosion process is mix-controlled by both activation and mass-transfer steps. Passivity can be developed on carbon steel in the soil at low temperatures. With the increase of temperature, the passive current density increases and the passive potential range decreases. When temperature is elevated to a certain value, 50 °C in this system, passivity cannot be maintained and the steel is dominated by an active dissolution status. Anodic Tafel slope decreases continuously with the increase in temperature, which is mainly due to the enhanced electrode reaction rate at an elevated temperature. Simultaneously, cathodic Tafel slope increases with temperature continuously due to the decrease of the solubility of dissolved oxygen in soil. Since the diffusion activation energy is generally much smaller than the reaction activation energy, the effect of temperature on diffusion is far less than that on electrode reaction rate.     

Cathodic activities of oxygen and hydrogen on carbon steel in simulated fuel-grade ethanol

Cathodic reactions, specially the oxygen and hydrogen activities, have been extensively investigated on carbon steel in simulated fuel-grade ethanol (SFGE) environments using cathodic potentiodynamic polarization and electrochemical impedance spectroscopy. Under normal conditions, oxygen reduction is the major cathodic reaction for carbon steel in SFGE. Hydrogen evolution, confirmed by hydrogen permeation test, is activated by de-aeration and at much higher cathodic overpotential. The dissociation of acetic acid in SFGE enhances the proton related cathodic reactions. Water in ethanol can increase the proton dissociation rate, resulting in a higher cathodic current density. At potentials close to free corrosion potential, the reduction of surface oxidized products contributes to the cathodic activities in SFGE. Based on this study, the possible effects of cathodic reactions on corrosion of carbon steel in SFGE are also discussed.     

Nanocrystallization of aluminized surface of carbon steel for enhanced resistances to corrosion and corrosive wear

Aluminizing is often used to improve steel's resistances to corrosion, oxidation and wear. This article reports our recent attempts to further improve aluminized carbon steel through surface nanocrystallization for higher resistances to corrosion and corrosive wear. The surface nanocrystallization was achieved using a process combining sandblasting and recovery heat treatment. The entire surface modification process includes dipping carbon steel specimens into a molten Al pool to form an Al coat, subsequent diffusion treatment at elevated temperature to form an aluminized layer, sandblasting to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. The grain size of the nanocrystallized aluminized surface layer was in the range of 20–100 nm. Electrochemical properties, electron work function (EWF), and corrosive wear of the nanocrystalline alloyed surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface of carbon steel exhibited improved resistances to corrosion, wear and corrosive wear. The passive film developed on the nanocrystallized aluminized surface was also evaluated in terms of its mechanical properties and adherence to the substrate.     

Electrochemical properties and corrosion protection of stainless steel for hot water tank

The state in which a stainless steel (STS) exhibits a very low corrosion rate is known as passivity, which is self-healing in a wide variety of environments. However, for those STS the corrosion includes pitting, crevice corrosion, galvanic corrosion, hydrogen embrittlement and stress corrosion cracking etc. And the corrosion resistance of STS is affected by area ratio, solution temperature and solution condition etc. Corrosion characteristics of STS 304, welding parts STS 316, STS 329 and STS 444 were investigated with parameters such as corrosion potential, galvanic current measurements, cathodic and anodic polarization behaviors as a function of area ratio and solution temperature in solution for hot water tank. It was found that galvanic current is affected by the area ratio, temperature and a kind of STS for hot water tank. Corrosion potential of welding part STS 316 was lower than that of STS 304, STS 329, STS 444 in solution for #1, #2 hot water tank. Therefore, it is suggested that the welding part STS 316 acts as anode for the other STSs. The amplitude of galvanic current between welding parts STS 316 and STS 304, STS 329, STS 444 in #1 solution is smaller than that in #2 solution. This is the reason that chloride ion quantity in #2 solution is more than that for #1 solution. And then welding part STS 316 corrodes easily by acting as anode compared to the other STS.     

Modification of 1018 carbon steel corrosion process in alkaline sour medium with a formulation of chemical corrosion inhibitors

This work is focused on researching corrosion mechanism modifications of 1018 carbon steel in alkaline sour medium (0.1 M (NH₄)₂S and 10 ppm CN⁻) using inhibitor formulation (IHF) composed of hydroxyoleic imidazoline (C₁₂H₄₂ON₂), HI, and aminoether (C₂₀H₂₈O₃N₂), AE. The accelerated formation of corrosion products was thereby carried out in the presence of the formulation alone and of each of its components separately; these films were subsequently characterized by electrochemical impedance spectroscopy and scanning electron microscopy. The study in the presence of the IHF components revealed that the films formed have different nature, because their physical and chemical properties such as thickness, porosity and (electronic and ionic) conductivity are determined by the media where they are grown. The film formed in the presence of HI has a homogeneous, non-porous topography that impairs the diffusion process of H⁰, in addition, its electronic conductivity is above that observed in the film formed with AE. Then, it was determined that the film formed with IHF presents some distinctive component characteristics which interact in a complementary way improving film passivity.     

Electrochemical investigations of naphthenic acid corrosion for carbon steel and the inhibitive effect by some ethoxylated fatty acids

The electrochemical behavior and corrosion of carbon steel in various types of naphthenic acid solutions have been studied by using cyclic voltammetry technique. The data reveal that the anodic excursion spans of carbon steel in naphthenic acid solution are characterized by the occurrence of a well-defined anodic peak (peak A), followed by a passive region. The passivation may be related to the formation and precipitation of oxide film on the electrode surface. The data reveal that increasing naphthenic acid concentration enhances the anodic peak current density (I_PA) and shifts its peak potential towards more positive values. The corrosion rate of carbon steel depended critically on the naphthenic acid types. The rate of the corrosion process increased with increasing in molar mass of naphthenic acid, reaching a maximum value in the presence of CHPA acid (C₉), and then decreased.

Potentiodynamic polarization measurements indicated that ethoxylated fatty acid derivatives have a strong effect on the corrosion behavior of the carbon steel in naphthenic acid solutions. The inhibition efficiency of these compounds was found to vary with their nature and concentration. The order of effectiveness of the inhibitors was OL(EO)₈₀ > OL(EO)₄₀ > OL(EO)_20. The adsorption of ethoxylated fatty acid on the carbon steel surface in naphthenic acid solutions was found to obey Frumkin isotherm and kinetic-thermodynamic model.     

Corrosion inhibition of carbon steel in hydrochloric acid by cationic arylthiophenes as new eco-friendly inhibitors: Experimental and quantum chemical study

This study describes the adsorption behavior of three arylthiophene derivatives namely: 2-(4-amidino-3-fluorophenyl)-5-[4-methoxy phenyl] thiophene dihydrochloride salt (MA-1217), 2-(4-amidinophenyl)-5-[4-chlorophenyl] thiophene dihydrochloride salt (MA-1316) and 2-(4-amidino-3-fluorophenyl)-5-[4-chlorophenyl]thiophene dihydrochloride salt (MA-1312) at C-steel in 1.0 mol·L^-1 HCl interface using experimental and theoretical studies. Electrochemical and mass loss measurements showed that the inhibition efficiency (IE) of the arylthiophene derivatives increases with increasing concentrations and exhibited maximum efficiency 89% at 21×10^-6 mol·L^-1 (MA-1217) by mass loss method. The investigated arylthiophene derivatives obey the Langmuir adsorption isotherm. From polarization studies the arylthiophene derivatives act as mixed-type inhibitors. Surface analysis were carried out and discussed. The mode of orientation and adsorption of inhibitor molecules on C-steel surface was studied using molecular dynamics (MD) simulations. Quantum chemical parameters as well as the radial distribution function indices and binding energies confirm the experimental results.     

Amine-based solvent for CO2 absorption and its impact on carbon steel corrosion: A perspective review

Carbon dioxide (CO₂) is one of the commonly emitted gaseous by-products in industrial processes. While CO₂ gas is the main cause to greenhouse effect, various CO₂ capture technologies have been proposed and implemented to sequester the CO₂ before the waste gases being released into the atmosphere. One of the mature technologies for CO₂ absorption is by using amine-based solvents. In this regard, different single amine solvents or blended amine solvents have been proven for their capability to remove CO₂. However, the dissolution and reaction of CO₂ gas with the amine solvents turn the solution corrosive. Such phenomenon is undesired as it posts corrosion problem to the absorption column, which normally built of carbon steel material. Henceforth, understanding the behaviour of different amine-based solvents in absorbing CO₂ and its subsequent impact on carbon steel corrosion is very significant. In this review article, we will outline some of the more commonly used solvents and their respective advantages and disadvantages, motivating further investigation into the corrosion tendency. Meanwhile, existing gaps in this research area are discussed for future investigation.     

pH、离子浓度、温度对20A碳钢在氯化钠溶液中电化学腐蚀行为的影响

报道通过电化学工作站、扫描电子显微镜、XRD衍射仪及原子分光光度仪研究pH、离子浓度、温度对20A碳钢腐蚀行为的影响。根据实验结果分析认为：室温（10℃C）,pH=8下,OH^-与Cl^-在材料表面发生竞争吸附,低浓度氯离子溶液中OH^-对材料的腐蚀起到了较好的抑制作用;在高浓度氯离子溶液中,Cl^-对OH^-的竞争取得优势,Cl^-的侵蚀作用破坏了OH对电极表面的保护,使得碳钢的腐蚀加剧;随着温度的升高,加速了溶液离子的扩散,使得OH^-对电极的保护遭受破坏,氯离子的迁入能力增强,导致碳钢的Rct递减,Icorr增大;在70℃、0．1mol／LCl^-溶液中挂片6h,试片表面可以看到明显的两层结构,外层为疏松的Fe3O4腐蚀产物,内层可能是Fe（OH）3。     

Opuntia-Ficus-Indica (Nopal) mucilage as a steel corrosion inhibitor in alkaline media

This paper presents results on the corrosion performance of reinforcing steel in alkaline media when dehydrated Opuntia Ficus Indica (Nopal) was used as an admixture. The dehydrated Nopal material was mixed with saturated calcium hydroxide (SCH) at 0.5, 1.0, and 2.0% by weight. Half cell potentials and Linear Polarization Resistance (LPR) measurements were performed at different time periods to characterize the corrosion inhibiting effect of the admixture. Results showed good corrosion inhibiting effect of dehydrated Nopal on reinforcing steel. The polarization resistance (R _P) value increased from an average of 40 kΩ cm² for regular chloride-contaminated SCH solution, to an average of 150 kΩ cm² for Nopal-added chloride-contaminated SCH solutions. The addition of Nopal led to the formation of a denser and more packed oxide/hydroxide surface layer on the steel surface that decreased corrosion activity. This oxide/hydroxide layer growth was confirmed from microscopic evaluation of the metal surface layer performed at the end of the experiment.     

Development of Poly(aniline-co-o-toluidine)/TiO2 nanocomposite coatings for low carbon steel corrosion in 3.5% NaCl solution

Chemical oxidative polymerization of aniline (AN) and o-toluidine (OT) for the synthesis of copolymer, Poly(AN-co-OT) and its composite with TiO₂ nanoparticles, Poly(AN-co-OT)/TiO₂ employing ammonium persulfate as an oxidant and HCl as an external dopant were carried out. The homopolymers, Polyaniline and Poly(o-toluidine) were also prepared by following similar method. The synthesized polymers were characterized with FTIR spectroscopy, XRD/SEM/TEM analysis. The anticorrosive coatings were synthesized in dimethyl sulfoxide solution by dissolving synthesized polymers, and then were applied on low-carbon steel (LCS) samples using epoxy binder. The anticorrosive potential of the polymer coatings containing copolymer, copolymer-nanocomposite and homopolymers on LCS was evaluated in 3.5% NaCl at a temperature of 30?°C by open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. It was observed that the nanocomposite coating increases the protection efficacy by providing better barrier properties against corrosion as compared with neat copolymer and homopolymers coatings. The morphology of the coatings before and after 60 days LCS immersion in 3.5% NaCl solution was determined using SEM.     

Effect of carbon nano-tubes on the corrosion resistance of alkyd coating immersed in sodium chloride solution

Effect of carbon nano-tubes (CNTs) on corrosion protection of carbon steel coated by alkyd resin and tested after immersion in 3.5% NaCl solution for different periods was evaluated by electrochemical impedance spectroscopy (EIS) measurements and scanning electron microscopy (SEM) investigations. Changes in the impedance characteristics of the systems were found to be greatly affected by the percentage of CNTs. Degradation of alkyd resin film without CNTs was observed after 72 h. On other hand no blisters, pin-holes and delamination were observed for alkyd resin containing 0.5% CNTs. It was found that CNTs improved the corrosion resistance and the adhesion strength of alkyd resin.     

Investigation of the corrosion protection of SiOx-like oxide films deposited by plasma-enhanced chemical vapor deposition onto carbon steel

The paper reports on the corrosion behavior of carbon steel coated with thin SiO_x-like oxide films. The SiO_x-like coatings were deposited by plasma-enhanced chemical vapor deposition (PECVD) and their thickness was varied between 20 and 200 nm. The coated carbon steel interfaces were investigated for their corrosion protection efficiency when immersed in an aqueous saline solution of 3% NaCl. FTIR measurements and electrochemical impedance spectroscopy (EIS) experiments revealed that thin SiO_x-like coating layers (20 nm thick) do not prevent the carbon steel from corrosion, while thicker silica layers (d ≥ 100 nm) protect efficiently carbon steel interfaces in highly saline media with a protection efficiency of about 96% for a 200 nm thick coating.     

Evaluation of some bipyridinium dihalides as inhibitors for low carbon steel corrosion in sulfuric acid solution

Inhibition of low carbon steel (LCS) corrosion in 0.5 M H₂SO₄ solution by three bipyridinium dihalides (TMbPyBr₂, HMbPyBr₂ and MPhbPyCl₂) was evaluated by potentiodynamic polarization curves, EIS and SEM techniques. The effectiveness of the inhibitors is ranked as follows: MPhbPyCl₂ ≅ TMbPyBr₂ > HMbPyBr₂. The compounds behave as mixed-type inhibitors and their adsorption on the steel surface obeys the Langmuir adsorption isotherm. EIS measurements indicate that charge transfer controls the corrosion of steel in the absence and presence of the inhibitors and the equivalent circuit R_e(R_ctQ_dl) represents the electrode/solution interface either at the corrosion potential or at −75 and 30 mV versus E_corr. The compounds show maximum inhibition efficiency at 35 °C. The mechanism of corrosion inhibition was discussed in the light of the molecular structure of the bipyridinium salts.     

Evaluation of electrochemical frequency modulation as a new technique for monitoring corrosion and corrosion inhibition of carbon steel in perchloric acid using hydrazine carbodithioic acid derivatives

Electrochemical frequency modulation, EFM is a new technique for corrosion rate measurements. With the EFM technique, the corrosion rate and corrosion kinetic parameters can be obtained instantaneously without prior knowledge of Tafel slopes, which makes this method an ideal technique for application as a corrosion monitoring tool. Results obtained with the EFM technique were shown to be in agreement with chemical (weight loss) and electrochemical methods (Tafel extrapolation and electrochemical impedance spectroscopy, EIS) for corrosion rate measurements. New synthesized hydrazine carbodithioic acid derivatives namely, N′-furan-2-yl-methylene-hydrazine carbodithioic acid (A), N′-(4-dimethylamino-benzylidene)-hydrazine carbodithioic acid (B) and N′-(3-nitro-benzylidene)-hydrazine carbodithioic acid (C) were examined as corrosion inhibitors for carbon steel in 1 M perchloric acid solution. The results obtained from both chemical and electrochemical measurements show that these compounds suppressed both anodic and cathodic processes of carbon steel corrosion in 1 M HClO₄ by adsorption on the electrode surface. The adsorption mode follows the Langmuir adsorption isotherm. The efficiency of the inhibitors increases in the order C > B > A.     

Electrochemical and AFM studies of mussel adhesive protein (Mefp-1) as corrosion inhibitor for carbon steel

Adsorption of mussel adhesive protein (Mefp-1) derived from the marine mussel Mytilus edulis and its corrosion inhibition for carbon steel were studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements in NaCl solutions at pH 4.6. The results indicate that the Mefp-1 confers significant corrosion inhibition of carbon steel, and the chloride concentration of the solution has an influence on the inhibition efficiency. Within a short exposure time, the inhibition efficiency is higher in the solution with a higher chloride concentration, whereas, for longer exposure time, up to one week, higher inhibition efficiency was obtained in the solution with a lower chloride concentration. AFM imaging was used both ex situ and in situ to investigate Mefp-1 adsorption. The in situ AFM measurements enable the protein adsorption on carbon steel to be visualized in real time in the solution. The AFM images illustrate how the Mefp-1 layer is formed on carbon steel. Measurements using bovine serum albumin (BSA) were also performed for comparison. The results showed that BSA also confers significant corrosion inhibition of carbon steel even though the BSA film formation process is slightly different from that of Mefp-1.     

Evaluation of corrosion and erosion-corrosion resistances of mild steel in sulfide-containing NaCl aerated solutions

This paper reports results of potentiodynamic polarization, electrochemical impedance measurements and erosion-corrosion of mild steel in aerated sulfide containing 3.5% NaCl solutions at room temperature. The pitting corrosion behavior was studied in NaCl solution containing 0.001, 0.005 and 0.010 M Na₂S, using potentiodynamic polarization and electrochemical impedance spectroscopy. The erosion-corrosion resistance was evaluated after rotating the samples in sulfide polluted NaCl solution for 24 h at a velocity of 300, 600 and 900 ppm using a rotating disc electrode. Results showed that the presence of sulfide ions in NaCl solution resulted in a significant increase in the corrosion attack due to the local acidification caused by iron sulfide formation. The localized replacement of the protective Fe-oxide film by a non-protective iron sulfide film is responsible for the pitting and erosion-corrosion attack. The study concluded that the higher the concentration of sulfide in NaCl solution, the lower the resistance to pitting and erosion-corrosion. Moreover, increasing the solution rotating velocity affects negatively the erosion-corrosion resistance.